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. Author manuscript; available in PMC: 2016 Apr 1.
Published in final edited form as: Nat Chem Biol. 2015 Aug 24;11(10):765–771. doi: 10.1038/nchembio.1891

Figure 7. CP binds Fe(II) with remarkably high affinity in a Ca(II)-dependent manner.

Figure 7

(a) ZP1 (1 µM) emission response to 3.5 µM Fe(II) in the absence (circles) and presence (squares) of 4 µM CP-Ser with addition of Ca(II). The red markers represent the 200-µM Ca(II) samples spiked with 4 µM Fe(II) (mean, n = 2). (b) ZP1 (1 µM) emission response to Fe(II) in the presence of 4 µM CP with or without 50 equiv of Ca(II) (mean ± SDM, n = 3). (c) Room-temperature EPR spectra of Mn(II) (black), CP-Ser in the presence of 50 equiv of Ca(II) and 0.9 equiv of Mn(II) (red), and CP-Ser in the presence of 50 equiv of Ca(II) and 0.9 equiv of Mn(II) with the addition of 0.9 equiv of Fe(II) (blue). (d) The concentration of free Mn(II) determined by room-temperature EPR (mean ± SDM, n = 3). (e) The concentration of unbound Fe(II) in ΔHis3Asp samples containing 0.9 equiv of Fe(II) after addition of 0.9 equiv of Zn(II) with and without 50 equiv of Ca(II) (mean ± SDM, n = 3). Control samples containing 25 µM protein, 0.9 equiv of Fe(II), and/or 50 equiv of Ca(II) are described in the right panel.